Colloquial :: Colloquial (a.) Pertaining to, or used in, conversation, esp. common and familiar conversation; conversational; hence, unstudied; informal; as, colloquial intercourse; colloquial phrases; a colloquial style..
Colloquialism :: Colloquialism (n.) A colloquial expression, not employed in formal discourse or writing..
Colloquialize :: Colloquialize (v. t.) To make colloquial and familiar; as, to colloquialize one's style of writing..